Block copolymer self assembly for design and vapor-phase synthesis of nanostructured antireflective surfaces

Abstract

The authors combine block copolymer self assembly with vapor-phase synthesis for design of antireflective thin film coatings. The nanometer-scale features in patterns formed by cylindrical phase block copolymers provide surface topography for vapor-phase growth of semiconductors and metals by oblique angle physical vapor deposition. The authors control the dimensions and density of the synthesized nanotextures through selection of copolymer molecular weight. A layer of aligned, densely packed germanium wire arrays with diameters much smaller than optical wavelengths acts as an effective optical medium, significantly reducing reflections and improving light coupling into a silicon substrate. A synthesized layer of uniformly sized silver nanoparticles provides antireflection instead through optical excitation of localized surface plasmons. The block copolymer-based synthesis approach allows control of particle shape anisotropy, tuning the frequency of plasmon resonances and expanding the spectral range of antireflection.